Expedient synthesis of two structurally close tetrasaccharides corresponding to the O-antigens of Escherichia coli O127 and Salmonella enterica O13

Article abstract of DOI:10.1016/j.tetasy.2012.08.006

Two structurally close tetrasaccharides corresponding to the O-antigens of Escherichia coli O127 and Salmonella enterica O13 have been synthesized using a 'unichemo' approach and minimum number of reaction steps. The yields of all glycosylation steps were excellent with a high stereochemical outcome. A common synthetic strategy has been adopted for the simultaneous synthesis of two tetrasaccharides.

Full text of DOI:10.1016/j.tetasy.2012.08.006

Tetrahedron: Asymmetry 23 (2012) 1385–1392
Contents lists available at SciVerse ScienceDirect
Tetrahedron: Asymmetry
journal homepage: www.elsevier.com/locate/tetasy
Expedient synthesis of two structurally close tetrasaccharides corresponding
to the O-antigens of Escherichia coli O127 and Salmonella enterica O13
⇑
Abhishek Santra , Tamashree Ghosh , Anup Kumar Misra
Bose Institute, Division of Molecular Medicine, P-1/12, C.I.T. Scheme VII-M, Kolkata 700054, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Two structurally close tetrasaccharides corresponding to the O-antigens of Escherichia coli O127 and Sal-
monella enterica O13 have been synthesized using a ‘unichemo’ approach and minimum number of reac-
tion steps. The yields of all glycosylation steps were excellent with a high stereochemical outcome. A
common synthetic strategy has been adopted for the simultaneous synthesis of two tetrasaccharides.
Ó 2012 Elsevier Ltd. All rights reserved.
Received 3 August 2012
Accepted 8 August 2012
Available online 14 September 2012
→2)-α-L-Fucp-(1→2)-β-D-Galp-(1→3)-α-D-GalpNAc-
(1→3)-α-D-GalpNAc-(1→
1. Introduction
Escherichia coli O127
Gastrointestinal infections causing diarrhoea are a serious
health concern in tropical countries.1 Diarrhoea is one of the lead-
ing causes for death in humans, particularly in children in the
developing countries.2,3 The microorganisms associated with sev-
eral food-borne and water-borne diarrhoeal outbreaks in develop-
ing and developed countries are enteropathogenic Escherichia coli
(E. coli), Salmonella enterica (S. enterica) and Shigella strains.4–6 Sev-
eral pathotypes of E. coli strains, responsible for gastrointestinal
infections are classified in several pathotypes, which include:
enteropathogenic E. coli (EPEC), enterotoxigenic E. coli (ETEC),
enteroinvasive E. coli (EIEC), enterohaemorrhagic E. coli (EHEC),
enteroaggregative E. coli (EAEC) and diffusely adherent E. coli
(DAEC).7 Among several virulent strains of E. coli, EPEC causes
acute infantile diarrhoea in the tropical countries.8 Similar to
enteropathogenic E. coli, Salmonella enterica strains are also associ-
ated with food and water borne diseases worldwide.9 Salmonella
infections are originated from infected poultry products and
household pets.10 Diarrhoea causing S. enterica strains are divided
into a subset of a number of serovars.11 These serovars have several
virulence features that help bacteria to cause diseases by various
mechanisms. Recently, Perepelov et al.12 established the chemical
structure of the repeating unit of the O-polysaccharide of Salmo-
nella enterica O13 and its relationship with the repeating unit of
the O-antigen of enteropathogenic E. coli O127. The O-antigen of
E. coli O127 is closely similar to the O-antigen of S. enterica O13,
→2)-α-L-Fucp-(1→2)-β-D-Galp-(1→3)-α-D-GalpNAc-
(1→3)-α-D-GlcpNAc-(1→
Salmonella enterica O13
Figure 1. Structures of the repeating units of the O-antigens of E. coli O127 and S.
enterica O13.
The emergence of multi-drug resistant microorganisms is a seri-
ous concern in the drug discovery research. In addition to the use
of established therapeutics for the treatment of microbial infec-
tions, the emergence of drug resistant bacterial strains forces
researchers to develop alternative approach to eradicate the infec-
tions.13 O-Polysaccharides (O-antigens) are well known for their
role in the pathogenicity of bacteria as well as their involvement
in the initial stages of bacterial infections.14,15 Several attempts
have been made to develop glycoconjugate vaccines16–19 derived
from cell wall polysaccharides of bacteria to combat against bacte-
rial infections. In order to develop glycoconjugate derivatives, it is
essential to have a significant quantity of the oligosaccharides in
hand, which are practically difficult to isolate them from their nat-
ural sources. In this context, the development of concise synthetic
strategies for the chemical synthesis of oligosaccharides can deli-
ver the required quantity of materials for their biological evalua-
tion. Since the structures of the O-antigens of E. coli O127 and S.
enterica O13 and their pathogenic actions are very close, it would
be worthwhile to develop concise chemical synthetic strategies
for the synthesis of both tetrasaccharide repeating units. Herein
we report an expedient synthesis of two structurally close tetrasac-
charides corresponding to the O-antigens of Escherichia coli O127
and Salmonella enterica O13 (Fig. 2).
which only differs in the presence of a
D
-GalpNAc moiety in place
of a
D-GlcpNAc moiety present in S. enterica O13 (Fig. 1).
⇑
Corresponding author. Tel.: +91 33 25693240; fax: +91 33 2355 3886.
E-mail address: akmisra69@gmail.com (A.K. Misra).
These two authors contributed equally to this work.
0957-4166/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tetasy.2012.08.006

1386
A. Santra et al. / Tetrahedron: Asymmetry 23 (2012) 1385–1392
HO
OH
O
HO
OH
A
O
O
AcHN
AcHN
OPMP
C
O
HO
B
O
O
OH
HO
O
D
OH
OH
HO
1
OH
O
HO
HO
OH
A
O
O
AcHN
AcHN
OPMP
C
O
HO
B
O
O
OH
HO
O
D
OH
OH
2
HO
PMP : p-Methoxyphenyl
Ph
Ph
Ph
O
O
O
O
O
O
O
O
O
HO
SEt
STol
BnO
AcO
N3
OAc
N3
PMPO
5
3
4
Ph
O
SEt
OBn
O
O
O
HO
OBn
N3
BnO
OPMP
7
6
Figure 2. Structures of tetrasaccharides 1 and 2 corresponding to the repeating units of the O-antigens of Escherichia coli O127 and Salmonella enterica O13 and their synthetic
precursors.
sis of two tetrasaccharides that is the use of similar protecting
groups during the synthesis and their removal in one step; (b)
the use of thioglycosides as glycosyl donors in all glycosylations;
(c) high stereoselectivity in product formation; (d) the preparation
of thioglycoside and p-methoxyphenyl glycosides of 2-azido-2-
deoxy sugar derivatives and their use in glycosylations; (e) the
use of a combination of perchloric acid supported over silica gel
(HClO4–SiO2)25 as a solid acid and N-iodosuccinimide as the thio-
philic activator26 in all glycosylations; (f) the one step removal of
benzylidene acetal, benzyl ethers and reduction of an azido group
using a combination of triethylsilane and Pearlman’s catalyst (20%
Pd(OH)2–C);27 and (g) the simultaneous synthesis of two tetrasac-
charides using similar reaction conditions.
2. Results and discussion
The synthesis of two tetrasaccharides
p-methoxyphenyl glycosides (Fig. 2) was achieved using stereose-
lective sequential glycosylations of differentially protected mono-
saccharide intermediates. The presence of
1 and 2 as their
a-D-galactosamine,
a-
D
-glucosamine and -fucose in both molecules poses extra
a-L
challenges in their chemical synthesis. In order to construct the
target compounds, a number of suitably protected monosaccharide
22
derivatives 3,20 4, 5,21
6
and 723 were prepared from the com-
mercially available reducing sugars using reaction methodologies
reported earlier. Compound 3 was prepared from tri-O-acetyl-
D
-galactal in six steps. Compound 4 was prepared from tri-O-acetyl-
-galactal in seven steps. Compound 5 was prepared from -galactose
-fucose in four steps
-glucosamine hydrochloride
1,3,4,6-Tetra-O-acetyl-2-azido-2-deoxy-a,b-D-galacto-pyranose
D
D
828 derived from
D-galactal, was treated with p-thiocresol in the
in six steps. Compound 6 was prepared from
and compound 7 was prepared from
L
presence of borontrifluoride diethyletherate in dichloromethane29
D
to give p-methylphenyl 3,4,6-tri-O-acetyl-2-azido-2-deoxy-1-thio-
b-D-galactopyranoside 9 together with its a-isomer 10 in 85% yield
in five steps. The notable features of the synthetic strategy include:
(a) application of a ‘unichemo protection strategy’24 for the synthe-

A. Santra et al. / Tetrahedron: Asymmetry 23 (2012) 1385–1392
1387
(
a
/b = 2:3), which was separated by column chromatography over
in CH2Cl2–Et2O furnished tetrasaccharide derivative 15 in 71%
yield together with a minor quantity (ꢀ5%) of its b-isomer, which
was separated by column chromatography. The stereoselective for-
mation of compound 15 was confirmed from its spectroscopic
analysis [signals at d 5.62 (d, J = 3.0 Hz, H-1A), 5.57 (d, J = 3.0 Hz,
H-1B), 5.47 (d, J = 3.0 Hz, H-1D), 4.76 (d, J = 8.0 Hz, H-1C) in the 1H
NMR and at d 102.4 (C-1C), 97.5 (C-1A), 97.2 (C-1B), 94.8 (C-1D) in
the 13C NMR spectra]. Removal of benzylidene acetals, benzyl
ethers and the reduction of the azido group in one step using tri-
ethylsilane in the presence of 20% Pd(OH)2–C27 followed by N-acet-
ylation using acetic anhydride in methanol furnished the fully
deprotected tetrasaccharide 1 as its p-methoxyphenyl glycoside
in 64% overall yield. The structure of tetrasaccharide 1 was unam-
biguously confirmed from its spectroscopic analysis [signals at d
5.39 (d, J = 3.5 Hz, H-1A), 5.12 (d, J = 4.0 Hz, H-1D), 4.99 (d,
J = 3.0 Hz, H-1B), 4.54 (d, J = 8.0 Hz, H-1C) in the 1H NMR and at d
102.1 (C-1C), 99.2 (C-1D), 97.1 (C-1A), 93.2 (C-1B) in the 13C NMR
spectra] (Scheme 2).
silica gel. Compound 9 was subjected to a series of functional
group transformation involving (a) the removal of the acetyl group
using sodium methoxide; (b) benzylidene acetal formation30 using
benzaldehyde dimethylacetal and p-toluenesulfonic acid; and (c)
acetylation using acetic anhydride and pyridine to give compound
4 in 86% yield (Scheme 1).
The stereoselective glycosylation of compound 3 with com-
pound 4 in the presence of a combination26 of N-iodosuccinimide
(NIS) and HClO4–SiO2 using dichloromethane–diethyl ether (1:1)
as the reaction solvent furnished disaccharide derivative 11 in
78% yield gave with a minor quantity (ꢀ6%) of its b-isomer, which
was separated by column chromatography. The stereoselective for-
mation of compound 11 was confirmed from spectroscopic analy-
sis [signals at d 5.64 (d, J = 3.0 Hz, H-1A), 5.40 (d, J = 3.5 Hz, H-1B) in
the 1H NMR and d 98.0 (C-1A), 95.4 (C-1B) in the 13C NMR spectra].
Saponification of compound 11 with sodium methoxide in metha-
nol resulted in the formation of disaccharide acceptor 12 in quan-
titative yield. The iodonium ion promoted glycosylation of
compound 12 with thioglycoside derivative 5 in the presence of
NIS and HClO4–SiO2 in dichloromethane afforded trisaccharide
derivative 13 in 83% yield, which was de-acetylated using sodium
methoxide to give trisaccharide acceptor 14 in 96% yield. The ster-
eoselective formation of compound 13 was confirmed from its
spectroscopic analysis [signals at d 5.61 (d, J = 3.0 Hz, H-1A), 5.39
(d, J = 3.5 Hz, H-1B), 4.73 (d, J = 8.0 Hz, H-1C) in the 1H NMR and d
102.2 (C-1C), 97.6 (C-1A), 94.7 (C-1B) in the 13C NMR spectra]. Gly-
cosylation of compound 14 with thioglycoside derivative 6 using
NIS and an HClO4–SiO2 combination as the glycosylation promoter
In another experiment, the iodonium ion promoted stereoselec-
tive glycosylation of compound 7 with compound 4 in the presence
26
of NIS and HClO4–SiO2 using dichloromethane–diethyl ether
(1:1) as the reaction solvent furnished exclusively disaccharide
derivative 16 in 73% yield. The formation of compound 16 was con-
firmed from its spectroscopic analysis [signals at d 5.60 (d,
J = 3.5 Hz, H-1B), 5.45 (d, J = 3.5 Hz, H-1A) in the 1H NMR and at d
99.7 (C-1B), 98.7 (C-1A) in the 13C NMR spectra]. Removal of the
O-acetyl group using sodium methoxide gave disaccharide accep-
tor 17 in quantitative yield. The stereoselective glycosylation of
compound 17 with thioglycoside derivative 5 in the presence of
NIS and HClO4–SiO2 in dichloromethane afforded trisaccharide
derivative 18 in 77% yield, which was de-acetylated using sodium
methoxide to give trisaccharide acceptor 19 in a quantitative yield.
The formation of compound 18 was confirmed from its spectro-
scopic analysis [d 5.67 (d, J = 3.0 Hz, H-1B), 5.49 (d, J = 3.0 Hz, H-
1A), 4.81 (d, J = 8.0 Hz, H-1C) in the 1H NMR and at d 101.7 (C-1C),
99.8 (C-1B), 98.5 (C-1A) in the 13C NMR spectra]. Glycosylation of
compound 19 with thioglycoside derivative 6 using NIS and an
HClO4–SiO2 combination26 as glycosylation promoter in CH2Cl2–
Et2O furnished tetrasaccharide derivative 20 in 75% yield together
with a minor quantity (ꢀ5%) of its b-isomer, which was separated
by column chromatography. The stereoselective formation of com-
pound 20 was confirmed from spectroscopic analysis [signals at d
5.63 (d, J = 3.0 Hz, H-1B), 5.50 (d, J = 3.5 Hz, H-1D), 5.45 (d,
J = 3.0 Hz, H-1A), 4.76 (d, J = 8.0 Hz, H-1C) in the 1H NMR and at d
102.3 (C-1C), 100.1 (C-1D), 98.5 (C-1B), 97.0 (C-1A) in the 13C NMR
spectra]. Removal of the benzylidene acetals, benzyl ethers and
the reduction of an azido group in one step using triethylsilane
in the presence of 20% Pd(OH)2–C27 followed by N-acetylation
using acetic anhydride in methanol furnished fully deprotected
tetrasaccharide 2 as its p-methoxyphenyl glycoside in 62% overall
yield. The structure of tetrasaccharide 2 was confirmed unambigu-
ously from its spectroscopic analysis [signals at d 5.30 (d, J = 3.5 Hz,
H-1A), 5.28 (d, J = 3.5 Hz, H-1B), 5.05 (d, J = 3.5 Hz, H-1D), 4.47 (d,
J = 7.5 Hz, H-1C) in the 1H NMR and at d 102.0 (C-1C), 99.3 (C-1D),
97.1 (C-1B), 96.8 (C-1A) in the 13C NMR] (Scheme 3).
AcO
OAc
O
AcO
OAc
N3
8
a
AcO
OAc
AcO
OAc
O
O
STol
AcO
AcO
+
N3
N3
STol
9
10
b, c, d
Ph
O
O
O
3. Conclusion
STol
AcO
N3
In conclusion, two structurally close tetrasaccharides corre-
sponding to the O-antigens of Escherichia coli O127 and Salmonella
enterica O13 have been synthesized using similar reaction condi-
tions by exploiting a ‘unichemo approach’ with a minimum num-
4
Scheme 1. Reagents and conditions: (a) p-thiocresol, BF3ꢁOEt2, CH2Cl2, 0 °C to room
temperature, 24 h, 85% (34% -isomer and 51% b-isomer); (b) 0.1 M CH3ONa,
CH3OH, room temperature, 4 h; (c) benzaldehyde dimethylacetal, p-TsOH, DMF,
room temperature, 24 h; (d) acetic anhydride, pyridine, room temperature, 2 h, 86%
over all yield.
a
ber of reaction steps. In both cases, high yields of
a-glycosides
were achieved using iodonium ion promoted thioglycoside activa-
tion in dichloromethane–diethyl ether as the reaction solvent.

1388
A. Santra et al. / Tetrahedron: Asymmetry 23 (2012) 1385–1392
Ph
Ph
O
O
O
O
A
a
O
7 + 4
O
N3
N3
OPMP
RO
O
B
A
O
a
O
3 + 4
N3
O
O
N3
OPMP
O
RO
B
16: R = Ac
17: R = H
b
Ph
O
O
11: R = Ac
12: R = H
b
Ph
c
5
Ph
Ph
O
O
O
O
c
5
O
A
O
Ph
O
N3
N3
C
OPMP
BnO
O
B
O
Ph
OR
O
O
O
O
O
C
O
A
O
O
O
N3
O
N3
Ph
OPMP
BnO
O
B
OR
18: R = Ac
19: R = H
b
O
O
Ph
6
a
13: R = Ac
14: R = H
Ph
b
Ph
O
O
O
O
A
O
O
O
O
N3
O
N3
6
a
OPMP
C
BnO
BnO
O
B
Ph
O
O
O
D
Ph
O
O
OBn
OBn
d, e
O
O
Ph
A
2
O
20
O
O
O
N3
O
N3
OPMP
C
PMP: p-Methoxyphenyl
O
BnO
B
Scheme 3. Reagents and conditions: (a) NIS, HClO4–SiO2, MS 4 Å, CH2Cl2–Et2O
(1:1), ꢂ18 °C, 1 h, 73% for compound 16 and 75% for compound 20; (b) 0.1 M
CH3ONa, CH3OH, room temperature, 2 h, quantitative; (c) NIS, HClO4–SiO2, MS 4 Å,
CH2Cl2, ꢂ30 °C, 1.5 h, 77%; (d) Et3SiH, 20% Pd(OH)2–C, CH2Cl2–CH3OH (1:1), room
temperature, 6 h; (e) acetic anhydride, CH3OH, room temperature, 1 h, 62%.
O
O
D
O
OBn
OBn
Ph
BnO
d, e
1
15
PMP: p-Methoxyphenyl
4. Experimental
Scheme 2. Reagents and conditions: (a) N-Iodosuccinimide (NIS), HClO4–SiO2, MS
4 Å, CH2Cl2–Et2O (1:1), ꢂ18 °C, 1 h, 78% for compound 11 and 71% for compound
15; (b) 0.1 M CH3ONa, CH3OH, room temperature, 2 h, quantitative for compound
12 and 96% for compound 14; (c) NIS, HClO4–SiO2, MS 4 Å, CH2Cl2, ꢂ30 °C, 1.5 h,
83%; (d) Et3SiH, 20% Pd(OH)2–C, CH2Cl2–CH3OH (1:1), room temperature, 6 h; (e)
acetic anhydride, CH3OH, room temperature, 1 h, 64%.
4.1. General methods
All reactions were monitored by thin layer chromatography
over silica gel coated TLC plates. The spots on TLC were visualized
by warming ceric sulphate (2% Ce(SO4)2 in 2 N H2SO4) sprayed
plates in a hotplate. Silica gel 230–400 mesh was used for column
chromatography. 1H and 13C NMR spectra were recorded on Bruc-
ker Avance 500 MHz using CDCl3 as solvent and TMS as internal
reference unless stated otherwise. Chemical shift value is ex-
pressed in d ppm. MALDI-MS were recorded on a Bruker Daltronics
Generalized glycosylation conditions have been applied in all gly-
cosylation reactions. All glycosylation reactions were high yielding
and highly stereoselective. Most of the synthetic intermediates
were solid and obtained in high yield.

A. Santra et al. / Tetrahedron: Asymmetry 23 (2012) 1385–1392
1389
mass spectrometer. Commercially available grades of organic sol-
vents of adequate purity were used in all reactions. HClO4–SiO2
was prepared following the literature reported method.25
(500 MHz, CDCl3): d 7.57–7.33 (m, 10H, Ar-H), 7.06 (d, J = 9.0 Hz,
2H, Ar-H), 6.84 (d, J = 9.0 Hz, 2H, Ar-H), 5.64 (d, J = 3.0 Hz, 1H, H-
1A), 5.62 (s, 1H, PhCH), 5.56 (s, 1H, PhCH), 5.43 (dd, J = 10.5,
3.5 Hz, 1H, H-3B), 5.40 (d, J = 3.5 Hz, 1H, H-1B), 4.57 (d, J = 3.0 Hz,
1H, H-4A), 4.49 (d, J = 3.0 Hz, 1H, H-4B), 4.46 (dd, J = 10.5, 3.5 Hz,
1H, H-3A), 4.35 (d, J = 12.5 Hz, 1H, H-6aA), 4.30 (d, J = 12.5 Hz, 1H,
H-6aB), 4.14 (d, J = 12.5 Hz, 1H, H-6bB), 4.10–4.06 (m, 2H, H-5B, H-
4.2. p-Methylphenyl 3-O-acetyl-2-azido-4,6-O-benzylidene-2-
deoxy-1-thio-b-D-galactopyranoside 4
To a solution of compound 8 (5.0 g, 13.39 mmol) in anhydrous
CH2Cl2 (30 mL) were added p-thiocresol (2.2 g, 17.71 mmol) and
BF3ꢁOEt2 (2.5 mL, 20.25 mmol) at 0 °C and the reaction mixture
was allowed to stir at room temperature for 24 h. The reaction
mixture was poured into satd NaHCO3 and extracted with CH2Cl2
(150 mL). The organic layer was washed with water, dried
(Na2SO4) and concentrated to give the crude product, which was
purified over SiO2 using hexane–EtOAc (8:1) as eluant to give p-
6bA), 4.01 (dd, J = 10.0, 3.0 Hz, 1H, H-2A), 3.98 (dd, J = 10.0, 3.0 Hz,
1H, H-2B), 3.87–3.86 (m, 1H, H-5A), 3.78 (s, 3H, OCH3), 2.15 (s,
3H, COCH3); 13C NMR (125 MHz, CDCl3): d 170.2 (COCH3), 155.4–
114.7 (Ar-C), 100.9 (PhCH), 100.8 (PhCH), 98.0 (C-1A), 95.4 (C-1B),
73.4 (C-4A), 71.6 (C-4B), 71.5 (C-3A), 69.3 (C-6B), 69.2 (C-6A), 68.9
(C-3B), 63.4 (C-5B), 63.3 (C-5A), 58.3 (C-2A), 56.6 (C-2B), 55.6
(OCH3), 20.9 (COCH3); MALDI-MS: 739.2 [M+Na]+; Anal. Calcd for
C35H36N6O11 (716.24): C, 58.65; H, 5.06. Found: C, 58.48; H, 5.20.
methylphenyl
3,4,6-tri-O-acetyl-2-azido-2-deoxy-1-thio-b-
D-
galactopyranoside 9 (3.0 g, 51%) and its
a
-isomer 10 (2.0 g, 34%).
4.4. p-Methoxyphenyl (2-azido-4,6-O-benzylidene-2-deoxy-
galactopyranosyl)-(1?3)-2-azido-4,6-O-benzylidene-2-deoxy-
-galactopyranoside 12
a-D-
A solution of compound 9 (3.0 g, 6.86 mmol) in 0.1 M CH3ONa
(25 mL) was stirred at room temperature for 4 h, neutralized with
Dowex 50W X8 (H+) resin, filtered and concentrated. To a solution
of the de-O-acetylated product in dry DMF (10 mL) were added
benzaldehyde dimethylacetal (1.3 mL, 8.66 mmol) and p-TsOH
(250 mg) and the reaction mixture was allowed to stir at room
temperature for 24 h. The reaction was quenched with Et3N
(1 mL) and the solvents were removed under reduced pressure to
give the crude product. A solution of the crude product in acetic
anhydride–pyridine (5 mL, 1:1, v/v) was kept at room temperature
for 2 h. The solvents were removed under reduced pressure and the
crude product was diluted with CH2Cl2 (100 mL). The organic layer
was successively washed with satd NaHCO3, water, dried (Na2SO4)
and concentrated to give the crude product, which was purified
over SiO2 using hexane–EtOAc (3:1) as eluant to give pure com-
a-D
A solution of compound 11 (1.3 g, 1.81 mmol) in 0.1 M CH3ONa
(15 mL) was allowed to stir at room temperature for 2 h. The reac-
tion mixture was neutralized with Dowex 50W X8 (H+) resin, fil-
tered and concentrated to give the crude product, which was
passed through a short pad of SiO2 using hexane–EtOAc (1:1) as
eluant to give pure compound 12 (1.2 g, 98%). White solid; mp
225–226 °C; ½a 2D5
¼ þ179 (c 1.2, CHCl3); IR (KBr): 3562, 2929,
ꢃ
2108, 1724, 1508, 1455, 1407, 1271, 1243, 1222, 1139, 1104,
1089, 1045, 1006, 959, 832, 810, 745, 699 cmꢂ1
;
1H NMR
(500 MHz, CDCl3): d 7.57–7.33 (m, 10H, Ar-H), 7.05 (d, J = 9.0 Hz,
2H, Ar-H), 6.81 (d, J = 9.0 Hz, 2H, Ar-H), 5.61 (s, 2H, 2 PhCH), 5.59
(d, J = 3.0 Hz, 1H, H-1A), 5.33 (d, J = 3.0 Hz, 1H, H-1B), 4.48 (br s,
1H, H-4A), 4.44 (dd, J = 10.5, 3.5 Hz, 1H, H-3A), 4.37 (d, J = 12.5 Hz,
1H, H-6aA), 4.35 (br s, 1H, H-4B), 4.30–4.25 (m, 2H, H-3B, H-6aB),
4.12 (d, J = 12.5 Hz, 1H, H-6bB), 4.09–4.06 (m, 1H, H-6bA), 4.01–
4.00 (m, 1H, H-5B), 3.98 (dd, J = 10.0, 3.0 Hz, 1H, H-2A), 3.85–3.84
(m, 1H, H-5A), 3.77 (s, 3H, OCH3), 3.61 (dd, J = 10.0, 3.0 Hz, 1H, H-
2B); 13C NMR (125 MHz, CDCl3): d 155.4–114.7 (Ar-C), 101.3
(PhCH), 100.8 (PhCH), 97.8 (C-1A), 95.7 (C-1B), 75.5 (C-4B), 71.8
(C-4A), 71.7 (C-3A), 69.3 (C-6A), 69.1 (C-6B), 66.7 (C-3B), 63.7 (C-
5A), 63.3 (C-5B), 60.0 (C-2A), 58.4 (C-2B), 55.5 (OCH3); ESI-MS:
697.2 [M+Na]+; Anal. Calcd for C33H34N6O10 (674.23): C, 58.75; H,
5.08. Found: C, 58.57; H, 5.25.
pound 4 (2.6 g, 86%). Yellow oil; ½a D25
¼ ꢂ43 (c 1.2, CHCl3); IR
ꢃ
(neat): 3445, 2113, 1748, 1634, 1369, 1245, 1233, 1092, 1043,
1023, 997, 808, 769, 705 cmꢂ1 1H NMR (500 MHz, CDCl3): d 7.60
;
(d, J = 8.0 Hz, 2H, Ar-H), 7.40–7.37 (m, 5H, Ar-H), 7.05 (d,
J = 8.0 Hz, 2H, Ar-H), 5.46 (s, 1H, PhCH), 4.77 (dd, J = 10.5, 3.5 Hz,
1H, H-3), 4.42 (d, J = 10.0 Hz, 1H, H-1), 4.36 (d, J = 12.5 Hz, 1H, H-
6a), 4.30 (d, J = 3.0 Hz, 1H, H-4), 3.99 (d, J = 12.5 Hz, 1H, H-6b),
3.78 (t, J = 10.0 Hz each, 1H, H-2), 3.54–3.53 (m, 1H, H-5), 2.34 (s,
3H, CH3), 2.10 (s, 3H, COCH3); 13C NMR (125 MHz, CDCl3): d
170.2 (COCH3), 138.6–126.1 (Ar-C), 100.9 (PhCH), 85.3 (C-1), 74.0
(C-3), 72.6 (C-4), 69.5 (C-5), 69.2 (C-6), 58.1 (C-2), 21.3 (CH3),
20.9 (COCH3); ESI-MS: 464.1 [M+Na]+; Anal. Calcd for C22H23N3O5S
(441.13): C, 59.85; H, 5.25. Found: C, 59.70; H, 5.50.
4.5. p-Methoxyphenyl (2-O-acetyl-3-O-benzyl-4,6-O-benzylid-
ene-b-
2-deoxy-
ene-2-deoxy-a-D
D
-galactopyranosyl)-(1?3)-(2-azido-4,6-O-benzylidene-
-galactopyranosyl)-(1?3)-2-azido-4,6-O-benzylid-
-galactopyranoside 13
4.3. p-Methoxyphenyl (3-O-acetyl-2-azido-4,6-O-benzylidene-2-
a-D
deoxy-a-D-galactopyranosyl)-(1?3)-2-azido-4,6-O-benzylidene-2-
deoxy-a-D-galactopyranoside 11
To a solution of compound 12 (1.0 g, 1.48 mmol) and compound
5 (760 mg, 1.71 mmol) in anhydrous CH2Cl2 (10 mL) were added
MS 4 Å (2 g) and the reaction mixture was allowed to stir at room
temperature under argon for 20 min. The reaction mixture was
cooled to ꢂ30 °C and to the cooled reaction mixture was added
NIS (450.0 mg, 2.0 mmol) followed by HClO4–SiO2 (15.0 mg) after
which the reaction mixture was allowed to stir at the same tem-
perature for 1.5 h. The reaction mixture was filtered through a Cel-
iteÒ bed and washed with CH2Cl2 (50 mL). The organic layer was
successively washed with 5% Na2S2O3, satd NaHCO3 and water,
dried (Na2SO4) and concentrated to a crude product, which was
purified over SiO2 using hexane–EtOAc (6:1) as eluant to give pure
compound 13 (1.3 g, 83%). White solid; mp 232–234 °C;
To a solution of compound 3 (1.0 g, 2.50 mmol) and compound
4 (1.2 g, 2.72 mmol) in a mixture of anhydrous CH2Cl2 (5 mL) and
Et2O (5 mL) were added MS 4 Å (2.0 g) and the reaction mixture
was allowed to stir at room temperature under argon for 20 min.
The reaction mixture was cooled to ꢂ18 °C and to the cooled reac-
tion mixture was added N-iodosuccinimide (NIS; 700.0 mg,
3.11 mmol) followed by HClO4–SiO2 (25.0 mg) after which the
reaction mixture was allowed to stir at the same temperature for
1 h. The reaction mixture was filtered through a CeliteÒ bed and
washed with CH2Cl2 (100 mL). The organic layer was washed suc-
cessively with 5% Na2S2O3, satd NaHCO3 and water, dried (Na2SO4)
and concentrated to a crude product, which was purified over SiO2
using hexane–EtOAc (6:1) as eluant to give pure compound 11
½
a 2D5
ꢃ
¼ þ147 (c 1.2, CHCl3); IR (KBr): 3446, 2920, 2871, 2112,
1743, 1454, 1406, 1396, 1225, 1148, 1110, 1083, 1052, 995, 695,
824, 803, 738, 700 cmꢂ1 1H NMR (500 MHz, CDCl3): d 7.58–7.30
(m, 20H, Ar-H), 7.05 (d, J = 9.0 Hz, 2H, Ar-H), 6.85 (d, J = 9.0 Hz,
(1.4 g, 78%). White solid; mp 68–70 °C; ½a D25
¼ þ224 (c 1.2, CHCl3);
ꢃ
IR (KBr): 3483, 2928, 2858, 2111, 1747, 1508, 1370, 1244, 1223,
;
1139, 1047, 1006, 955, 828, 805, 750, 700 cmꢂ1
;
1H NMR

1390
A. Santra et al. / Tetrahedron: Asymmetry 23 (2012) 1385–1392
2H, Ar-H), 5.63 (s, 1H, PhCH), 5.62 (s, 1H, PhCH), 5.61 (d, J = 3.0 Hz,
1H, H-1A), 5.46 (s, 1H, PhCH), 5.42 (dd, J = 8.0 Hz each, 1H, H-2C),
5.39 (d, J = 3.5 Hz, 1H, H-1B), 4.73 (d, J = 8.0 Hz, 1H, H-1C), 4.70–
4.62 (2 d, J = 12.5 Hz each, 2H, PhCH2), 4.57 (d, J = 2.5 Hz, 1H, H-
4A), 4.52 (d, J = 2.5 Hz, 1H, H-4B), 4.46 (dd, J = 10.5, 3.5 Hz, 1H, H-
3A), 4.35–4.28 (m, 3H, H-3B, H-6aA, H-6aC), 4.24 (d, J = 12.5 Hz,
1H, H-6aB), 4.14 (d, J = 3.0 Hz, 1H, H-4C), 4.12–4.07 (m, 3H, H-2A,
H-6bB, H-6bC), 4.00 (d, J = 12.5 Hz, 1H, H-6bA), 3.92 (br s, 1H, H-
5B), 3.90 (dd, J = 10.0, 3.0 Hz, 1H, H-2B), 3.86 (br s, 1H, H-5A), 3.78
(s, 3H, OCH3), 3.59 (dd, J = 10.5, 3.5 Hz, 1H, H-3C), 3.36 (br s, 1H,
H-5C), 2.03 (s, 3H, COCH3); 13C NMR (125 MHz, CDCl3): d 169.4
(COCH3), 155.4–114.7 (Ar-C), 102.2 (C-1C), 101.2 (PhCH), 100.8
(PhCH), 100.6 (PhCH), 97.6 (C-1A), 94.7 (C-1B), 77.5 (C-3C), 76.0
(C-4A), 73.8 (C-4C), 73.2 (C-3B), 71.2 (PhCH2), 71.1 (C-4B), 70.8
(C-2C), 70.2 (C-3A), 69.3 (C-6C), 69.2 (C-6A), 69.1 (C-6B), 66.6
(C-5C), 64.2 (C-5B), 63.2 (C-5A), 58.7 (C-2A), 58.5 (C-2B), 55.7
(OCH3), 20.9 (COCH3); MALDI-MS: 1079.3 [M+Na]+; Anal. Calcd
for C55H56N6O16 (1056.37): C, 62.49; H, 5.34. Found: C, 62.30; H,
5.55.
was allowed to stir at the same temperature for 1 h. The reaction
mixture was filtered through a CeliteÒ bed and washed with
CH2Cl2 (50 mL). The organic layer was successively washed with
5% Na2S2O3, satd NaHCO3 and water, dried (Na2SO4) and concen-
trated to a crude product, which was purified over SiO2 using hex-
ane–EtOAc (6:1) as eluant to give pure compound 15 (1.0 g, 71%).
White solid; mp 128–130 °C; ½a D25
¼ þ99 (c 1.2, CHCl3); IR (KBr):
ꢃ
3448, 3032, 2907, 2864, 2109, 1507, 1455, 1402, 1365, 1246,
1213, 1173, 1108, 1051, 1027, 806, 736, 697 cmꢂ1
;
1H NMR
(500 MHz, CDCl3): d 7.57–7.16 (m, 35H, Ar-H), 7.06 (d, J = 9.0 Hz,
2H, Ar-H), 6.83 (d, J = 9.0 Hz, 2H, Ar-H), 5.63 (s, 2H, 2 PhCH), 5.62
(d, J = 3.0 Hz, 1H, H-1A), 5.57 (d, J = 3.0 Hz, 1H, H-1B), 5.47 (d,
J = 3.0 Hz, 1H, H-1D), 5.37 (s, 1H, PhCH), 4.84 (d, J = 11.5 Hz, 1H,
PhCH2), 4.78 (d, J = 11.5 Hz, 1H, PhCH2), 4.76 (d, J = 8.0 Hz, 1H, H-
1C), 4.70–4.53 (m, 7H, H-3D, PhCH2), 4.52–4.46 (m, 2H, H-3A, H-
4A), 4.45–4.40 (m, 2H, H-4B, H-5D), 4.32–4.29 (m, 2H, H-6aA, H-
6aC), 4.23–4.19 (m, 3H, H-2A, H-4D, H-6aB), 4.17–4.10 (m, 2H, H-
6bA, H-6bC), 4.06 (d, J = 3.0 Hz, 1H, H-4C), 4.02–3.95 (m, 4H, H-2C,
H-2D, H-3B, H-6bB), 3.86 (br s, 1H, H-5A), 3.78 (s, 3H, OCH3), 3.77–
3.75 (m, 1H, H-3C), 3.71 (dd, J = 10.0, 3.0 Hz, 1H, H-2B), 3.48 (br s,
1H, H-5B), 3.32 (br s, 1H, H-5C), 0.86 (d, J = 3.0 Hz, 3H, CCH3); 13C
NMR (125 MHz, CDCl3): d 155.8–114.7 (Ar-C), 102.4 (C-1C), 100.9
(2 C, 2 PhCH), 100.8 (PhCH), 97.5 (C-1A), 97.2 (C-1B), 94.8 (C-1D),
81.6 (C-3C), 79.5 (C-2D), 78.5 (C-5B), 76.5 (C-3D), 75.8 (C-3B), 74.7
(PhCH2), 72.9 (PhCH2), 72.7 (C-4D), 72.3 (PhCH2), 71.8 (C-4B), 71.7
(C-4C), 71.0 (C-3A), 70.9 (C-4A), 70.8 (PhCH2), 69.3 (C-6C), 69.1 (C-
6A), 69.0 (C-6B), 66.4 (C-5D), 66.3 (C-5C), 64.3 (C-2C), 63.1 (C-5A),
58.9 (C-2A), 58.4 (C-2B), 55.6 (OCH3), 16.3 (CCH3); MALDI-MS:
1453.5 [M+Na]+; Anal. Calcd for C80H82N6O19 (1430.56): C, 67.12;
H, 5.77. Found: C, 66.94; H, 6.00.
4.6. p-Methoxyphenyl (3-O-benzyl-4,6-O-benzylidene-b-
opyranosyl)-(1?3)-(2-azido-4,6-O-benzylidene-2-deoxy-
galactopyranosyl)-(1?3)-2-azido-4,6-O-benzylidene-2-deoxy-
-galactopyranoside 14
D-galact
a-D-
a-D
A solution of compound 13 (1.2 g, 1.13 mmol) in 0.1 M CH3ONa
(15 mL) was allowed to stir at room temperature for 2 h. The reac-
tion mixture was neutralized with Dowex 50W X8 (H+) resin, fil-
tered and concentrated to give the crude product which was
passed through a short pad of SiO2 using hexane–EtOAc (1:1) as
eluant to give pure compound 14 (1.1 g, 96%). White solid; mp
238–240 °C; ½a 2D5
ꢃ
¼ þ190 (c 1.2, CHCl3); IR (KBr): 3483, 2914,
4.8. p-Methoxyphenyl (3-O-acetyl-2-azido-4,6-O-benzylidene-2-
2861, 2110, 1507, 1454, 1403, 1366, 1247, 1214, 1175, 1111,
deoxy-
ene-2-deoxy-a-D
a
-
D
-galactopyranosyl)-(1?3)-2-azido-4,6-O-benzylid-
-glucopyranoside 16
1087, 1048, 1025, 999, 806, 752, 699 cmꢂ1
;
1H NMR (500 MHz,
CDCl3): d 7.57–7.28 (m, 20 Hz, Ar-H), 7.04 (d, J = 9.0 Hz, 2H, Ar-
H), 6.83 (d, J = 9.0 Hz, 2H, Ar-H), 5.60 (s, 1H, PhCH), 5.59 (s, 1H,
PhCH), 5.58 (d, J = 3.0 Hz, 1H, H-1A), 5.43 (s, 1H, PhCH), 5.41 (d,
J = 3.0 Hz, 1H, H-1B), 4.82–4.73 (2 d, J = 12.5 Hz each, 2H, PhCH2),
4.57 (d, J = 2.5 Hz, 1H, H-4A), 4.55 (d, J = 8.0 Hz, 1H, H-1C), 4.47
(br s, 1H, H-4B), 4.43 (dd, J = 10.0, 3.0 Hz, 1H, H-3A), 4.36 (dd,
J = 10.0, 3.0 Hz, 1H, H-3B), 4.32 (d, J = 12.0 Hz, 1H, H-6aC), 4.28 (d,
J = 12.0 Hz, 1H, H-6aA), 4.23 (d, J = 12.0 Hz, 1H, H-6aB), 4.10–4.03
(m, 5H, H-2A, H-2C, H-4C, H-6bB, H-6bC), 4.00–3.97 (m, 2H, H-2B,
H-6bA), 3.93 (br s, 1H, H-5B), 3.79 (br s, 1H, H-5A), 3.76 (s, 3H,
OCH3), 3.48 (dd, J = 10.0, 3.0 Hz, 1H, H-3C), 3.29 (br s, 1H, H-5C);
13C NMR (125 MHz, CDCl3): d 155.4–114.7 (Ar-C), 104.3 (C-1C),
101.0 (PhCH), 100.9 (PhCH), 100.8 (PhCH), 97.6 (C-1A), 94.7 (C-
1B), 78.7 (C-3C), 76.2 (C-4A), 73.8 (C-4C), 73.6 (C-3B), 71.9 (PhCH2),
71.1 (C-4B), 71.0 (C-2C), 70.4 (C-3A), 69.2 (3 C, C-6A, C-6B, C-6C), 66.7
(C-5C), 64.2 (C-5B), 63.2 (C-5A), 58.7 (C-2B), 58.5 (C-2A), 55.6
(OCH3); MALDI-MS: 1037.3 [M+Na]+; Anal. Calcd for C53H54N6O15
(1014.36): C, 62.71; H, 5.36. Found: C, 62.50; H, 5.55.
To a solution of compound 7 (1.0 g, 2.5 mmol) and compound 4
(1.2 g, 2.72 mmol) in a mixture of anhydrous CH2Cl2 (5 mL) and
Et2O (5 mL) were added MS 4 Å (2.0 g) and the reaction mixture
was allowed to stir at room temperature under argon for 20 min.
The reaction mixture was cooled to ꢂ18 °C and to the cooled reac-
tion mixture was added NIS (700.0 mg, 3.11 mmol) followed by
HClO4–SiO2 (25.0 mg) after which the reaction mixture was al-
lowed to stir at the same temperature for 1 h. The reaction mixture
was filtered through a CeliteÒ bed and washed with CH2Cl2
(100 mL). The organic layer was successively washed with 5%
Na2S2O3, satd NaHCO3 and water, dried (Na2SO4) and concentrated
to a crude product, which was purified over SiO2 using hexane–
EtOAc (6:1) as eluant to give pure compound 16 (1.3 g, 73%). White
solid; mp 204–205 °C; ½a D25
¼ þ250 (c 1.2, CHCl3); IR (KBr): 3483,
ꢃ
2928, 2858, 2111, 1747, 1508, 1370, 1244, 1223, 1139, 1047,
1006, 955, 828, 805, 750, 700 cmꢂ1 1H NMR (500 MHz, CDCl3): d
;
7.42–7.28 (m, 10H, Ar-H), 6.98 (d, J = 9.0 Hz, 2H, Ar-H), 6.77 (d,
J = 9.0 Hz, 2H, Ar-H), 5.60 (d, J = 3.5 Hz, 1H, H-1B), 5.54 (s, 1H,
PhCH), 5.46 (s, 1H, PhCH), 5.45 (d, J = 3.5 Hz, 1H, H-1A), 5.35 (dd,
J = 10.0, 3.0 Hz, 1H, H-3B), 4.48 (t, J = 10.0 Hz each, 1H, H-3A), 4.40
(d, J = 3.5 Hz, 1H, H-4B), 4.30 (d, J = 11.5 Hz, 1H, H-6aA), 4.21 (dd,
J = 10.5, 5.0 Hz, 1H, H-6aB), 4.05–4.01 (m, 3H, H-5A, H-5B, H-6bA),
3.80 (t, J = 9.5 Hz each, 1H, H-4A), 3.77 (dd, J = 10.0, 3.0 Hz, 1H, H-
2B), 3.72 (s, 3H, OCH3), 3.70 (t, J = 10.5 Hz each, 1H, H-6bB), 3.21
(dd, J = 10.0, 3.0 Hz, 1H, H-2A), 2.11 (s, 3H, COCH3); 13C NMR
(125 MHz, CDCl3): d 170.4 (COCH3), 155.4–114.8 (Ar-C), 101.7
(PhCH), 100.7 (PhCH), 99.7 (C-1B), 98.7 (C-1A), 82.1 (C-4A), 73.6
(C-3A), 73.3 (C-4B), 69.4 (C-6B), 68.6 (C-6A), 68.5 (C-3B), 63.2 (C-
5B), 63.0 (C-5A), 61.4 (C-2A), 56.9 (C-2B), 55.6 (OCH3), 20.9 (COCH3);
ESI-MS: 739.2 [M+Na]+; Anal. Calcd for C35H36N6O11 (716.24): C,
58.65; H, 5.06. Found: C, 58.47; H, 5.25.
4.7. p-Methoxyphenyl (2,3,4-tri-O-benzyl-
(1?2)-(3-O-benzyl-4,6-O-benzylidene-b- -galactopyranosyl)-
(1?3)-(2-azido-4,6-O-benzylidene-2-deoxy- -galacto-
a-L-fucopyranosyl)-
D
a-D
pyranosyl)-(1?3)-2-azido-4,6-O-benzylidene-2-deoxy-a-D-
galactopyranoside 15
To a solution of compound 14 (1.0 g, 0.98 mmol) and compound
6 (550.0 mg, 1.15 mmol) in a mixture of anhydrous CH2Cl2 (4 mL)
and Et2O (4 mL) were added MS 4 Å (1.5 g) and the reaction mix-
ture was allowed to stir at room temperature under argon for
20 min. The reaction mixture was cooled to ꢂ18 °C and to the
cooled reaction mixture was added NIS (300.0 mg, 1.33 mmol) fol-
lowed by HClO4–SiO2 (10.0 mg) after which the reaction mixture

A. Santra et al. / Tetrahedron: Asymmetry 23 (2012) 1385–1392
1391
4.9. p-Methoxyphenyl (2-azido-4,6-O-benzylidene-2-deoxy-
galactopyranosyl)-(1?3)-2-azido-4,6-O-benzylidene-2-deoxy-
-glucopyranoside 17
a
-
D-
[M+Na]+; Anal. Calcd for C55H56N6O16 (1056.37): C, 62.49; H,
5.34. Found: C, 62.28; H, 5.57.
a-D
4.11. p-Methoxyphenyl (3-O-benzyl-4,6-O-benzylidene-b-
galactopyranosyl)-(1?3)-(2-azido-4,6-O-benzylidene-2-deoxy-
-galactopyranosyl)-(1?3)-2-azido-4,6-O-benzylidene-2-
deoxy- -glucopyranoside 19
D-
A solution of compound 16 (1.2 g, 1.67 mmol) in 0.1 M CH3ONa
(15 mL) was allowed to stir at room temperature for 2 h. The reac-
tion mixture was neutralized with Dowex 50W X8 (H+) resin, fil-
tered and concentrated to give the crude product which was
passed through a short pad of SiO2 using hexane–EtOAc (1:1) as
eluant to give pure compound 17 (1.1 g, 98%). White solid; mp
a-D
a
-D
A solution of compound 18 (1.1 g, 1.04 mmol) in 0.1 M CH3ONa
(15 mL) was allowed to stir at room temperature for 2 h. The reac-
tion mixture was neutralized with Dowex 50W X8 (H+) resin, fil-
tered and concentrated to give the crude product which was
passed through a short pad of SiO2 using hexane–EtOAc (1:1) as
eluant to give pure compound 19 (1.0 g, 99%). Colourless oil;
223–224 °C; ½a 2D5
¼ þ248 (c 1.2, CHCl3); IR (KBr): 3562, 2929,
ꢃ
2108, 1724, 1508, 1455, 1407, 1271, 1243, 1222, 1139, 1104,
1089, 1045, 1006, 959, 832, 810, 745, 699 cmꢂ1
;
1H NMR
(500 MHz, CDCl3): d 7.49–7.25 (m, 10H, Ar-H), 7.04 (d, J = 9.0 Hz,
2H, Ar-H), 6.85 (d, J = 9.0 Hz, 2H, Ar-H), 5.63 (d, J = 3.5 Hz, 1H, H-
1B), 5.62 (s, 1H, PhCH), 5.57 (s, 1H, PhCH), 5.51 (d, J = 3.5 Hz, 1H,
H-1A), 4.53 (d, J = 9.5 Hz each, 1H, H-3A), 4.38 (d, J = 12.5 Hz, 1H,
H-6aA), 4.34 (d, J = 3.5 Hz, 1H, H-4B), 4.27 (dd, J = 10.5, 5.0 Hz, 1H,
H-6aB), 4.24–4.19 (m, 1H, H-5A), 4.13–4.07 (m, 3H, H-3B, H-5B, H-
½
a 2D5
ꢃ
¼ þ106 (c 1.2, CHCl3); IR (neat): 3483, 2914, 2861, 2110,
1507, 1454, 1403, 1366, 1247, 1214, 1175, 1111, 1087, 1048,
1025, 999, 806, 752, 699 cmꢂ1 1H NMR (500 MHz, CDCl3): d
;
7.44–7.18 (m, 20H, Ar-H), 6.97 (d, J = 9.0 Hz, 2H, Ar-H), 6.78 (d,
J = 9.0 Hz, 2H, Ar-H), 5.63 (d, J = 3.5 Hz, 1H, H-1B), 5.52 (s, 1H,
PhCH), 5.51 (s, 1H, PhCH), 5.43 (d, J = 3.0 Hz, 1H, H-1A), 5.38 (s,
1H, PhCH), 4.76–4.68 (2 d, J = 12.5 Hz each, 2H, PhCH2), 4.52 (d,
J = 8.0 Hz, 1H, H-1C), 4.51–4.46 (m, 2H, H-3A, H-4B), 4.29–4.13 (m,
4H, H-5A, H-6aA, H-6aB, H-6aC), 4.05–3.99 (m, 4H, H-2C, H-5B, H-
6
bA), 3.87 (t, J = 9.5 Hz each, 1H, H-4A), 3.78 (s, 3H, OCH3), 3.77 (t,
J = 10.5 Hz each, 1H, H-6bB), 3.52 (dd, J = 10.0, 3.0 Hz, 1H, H-2B),
3.29 (dd, J = 10.0, 3.0 Hz, 1H, H-2A); 13C NMR (125 MHz, CDCl3): d
155.7–114.8 (Ar-C), 101.7 (PhCH), 101.2 (PhCH), 99.7 (C-1B), 98.5
(C-1A), 82.3 (C-4A), 75.5 (C-4B), 73.1 (C-3A), 69.5 (C-6B), 68.6 (C-
6A), 66.7 (C-5A), 63.4 (C-3B), 63.0 (C-5B), 61.7 (C-2A), 60.3 (C-2B),
55.6 (OCH3); ESI-MS: 697.2 [M+Na]+; Anal. Calcd for C33H34N6O10
(674.23): C, 58.75; H, 5.08. Found: C, 58.58; H, 5.27.
6bA, H-6bC), 3.96–3.93 (m, 2H, H-3B, H-4C), 3.82 (dd, J = 10.0,
3.0 Hz, 1H, H-2B), 3.79 (t, J = 9.5 Hz each, 1H, H-4A), 3.71 (s, 3H,
OCH3), 3.68 (t, J = 10.5 Hz each, 1H, H-6bB), 3.45 (dd, J = 10.0,
3.0 Hz, 1H, H-3C), 3.33 (br s, 1H, H-5C), 3.01 (dd, J = 10.0, 3.0 Hz,
1H, H-2A); 13C NMR (125 MHz, CDCl3): d 155.7–114.8 (Ar-C),
104.3 (C-1C), 101.8 (PhCH), 101.1 (PhCH), 100.8 (PhCH), 99.4 (C-
1B), 98.5 (C-1A), 82.4 (C-4A), 78.6 (C-3C), 76.1 (C-4B), 73.7 (2 C, C-
3A, C-4C), 72.6 (C-5A), 71.9 (PhCH2), 70.3 (C-2C), 69.4 (C-6C), 69.2
(C-6A), 68.6 (C-6B), 66.8 (C-5C), 63.8 (C-3B), 63.0 (C-5B), 61.8 (C-
2A), 58.6 (C-2B), 55.6 (OCH3); MALDI-MS: 1037.3 [M+Na]+; Anal.
Calcd for C53H54N6O15 (1014.36): C, 62.71; H, 5.36. Found: C,
62.50; H, 5.58.
4.10. p-Methoxyphenyl (2-O-acetyl-3-O-benzyl-4,6-O-benzyli-
dene-b-
2-deoxy-
ene-2-deoxy-
D
-galactopyranosyl)-(1?3)-(2-azido-4,6-O-benzylidene-
-galactopyranosyl)-(1?3)-2-azido-4,6-O-benzylid-
-glucopyranoside 18
a
-D
a
-D
To a solution of compound 17 (1.0 g, 1.48 mmol) and compound
5 (790.0 mg, 1.77 mmol) in anhydrous CH2Cl2 (10 mL) were added
MS 4 Å (1.5 g) and the reaction mixture was allowed to stir at room
temperature under argon for 20 min. The reaction mixture was
cooled to ꢂ30 °C and to the cooled reaction mixture was added
NIS (450.0 mg, 2.0 mmol) followed by HClO4–SiO2 (15.0 mg) after
which the reaction mixture was allowed to stir at the same tem-
perature for 1.5 h. The reaction mixture was filtered through a Cel-
iteÒ bed and washed with CH2Cl2 (50 mL). The organic layer was
successively washed with 5% Na2S2O3, satd NaHCO3 and water,
dried (Na2SO4) and concentrated to a crude product, which was
purified over SiO2 using hexane–EtOAc (6:1) as eluant to give pure
compound 18 (1.2 g, 77%). White solid; mp 209–210 °C;
4.12. p-Methoxyphenyl (2,3,4-tri-O-benzyl-
(1?2)-(3-O-benzyl-4,6-O-benzylidene-b- -galactopyranosyl)-
(1?3)-(2-azido-4,6-O-benzylidene-2-deoxy- -galactopyran-
-glucopy-
a-L-fucopyranosyl)-
D
a-D
osyl)-(1?3)-2-azido-4,6-O-benzylidene-2-deoxy-a-D
ranoside 20
To a solution of compound 19 (900.0 mg, 0.89 mmol) and com-
pound 6 (500.0 mg, 1.04 mmol) in a mixture of anhydrous CH2Cl2
(4 mL) and Et2O (4 mL) were added MS 4 Å (1.0 g) and the reaction
mixture was allowed to stir at room temperature under argon for
20 min. The reaction mixture was cooled to ꢂ18 °C and to the
cooled reaction mixture was added NIS (260.0 mg, 1.15 mmol) fol-
lowed by HClO4–SiO2 (10.0 mg) after which the reaction mixture
was allowed to stir at the same temperature for 1 h. The reaction
mixture was filtered through a CeliteÒ bed and washed with
CH2Cl2 (mL). The organic layer was successively washed with 5%
Na2S2O3, satd NaHCO3 and water, dried (Na2SO4) and concentrated
to a crude product, which was purified over SiO2 using hexane–
EtOAc (6:1) as eluant to give pure compound 20 (950.0 mg, 75%).
½
a 2D5
ꢃ
¼ þ118 (c 1.2, CHCl3); IR (KBr): 3446, 2920, 2871, 2112,
1743, 1454, 1406, 1396, 1225, 1148, 1110, 1083, 1052, 995, 824,
803, 738, 700 cmꢂ1 1H NMR (500 MHz, CDCl3): d 7.51–7.25 (m,
;
20H, Ar-H), 7.04 (d, J = 9.0 Hz, 2H, Ar-H), 6.85 (d, J = 9.0 Hz, 2H,
Ar-H), 5.67 (d, J = 3.0 Hz, 1H, H-1B), 5.60 (s, 1H, PhCH), 5.57 (s,
1H, PhCH), 5.49 (d, J = 3.0 Hz, 1H, H-1A), 5.46 (s, 1H, PhCH), 5.40
(t, J = 8.5 Hz each, 1H, H-2C), 4.81 (d, J = 8.0 Hz, 1H, H-1C), 4.69–
4.61 (2 d, J = 12.5 Hz each, 2H, PhCH2), 4.56 (t, J = 9.5 Hz each, 1H,
H-3A), 4.52 (br s, 1H, H-4B), 4.36–4.31 (m, 3H, H-5A, H-6aA, H-
6
aC), 4.26 (dd, J = 10.5, 5.0 Hz, 1H, H-6aB), 4.16 (d, J = 2.5 Hz, 1H,
Colourless oil; ½a D25
¼ ꢂ1 (c 1.2, CHCl3); IR (neat): 3448, 3032,
ꢃ
H-4C), 4.10–4.00 (m, 4H, H-3B, H-5B, H-6bA H-6bC), 3.85 (t,
,
2907, 2864, 2109, 1507, 1455, 1402, 1365, 1246, 1213, 1173,
J = 9.5 Hz each, 1H, H-4A), 3.78 (s, 3H, OCH3), 3.77–3.73 (m, 2H,
H-2B, H-6bB), 3.61 (dd, J = 10.0, 3.0 Hz, 1H, H-3C), 3.43 (br s, 1H,
H-5C), 3.24 (dd, J = 10.0, 3.0 Hz, 1H, H-2A), 2.00 (s, 3H, COCH3);
13C NMR (125 MHz, CDCl3): d 169.4 (COCH3), 155.7–114.8 (Ar-C),
101.7 (C-1C), 101.4 (PhCH), 101.3 (PhCH), 100.5 (PhCH), 99.8 (C-
1B), 98.5 (C-1A), 82.3 (C-4A), 77.5 (C-3C), 75.8 (C-4B), 73.2 (C-4C),
72.7 (C-3A), 72.3 (C-5A), 71.2 (PhCH2), 70.2 (C-2C), 69.4 (C-6C),
69.1 (C-6A), 68.6 (C-6B), 66.7 (C-5C), 63.9 (C-3B), 63.0 (C-5B), 61.7
(C-2A), 58.5 (C-2B), 55.6 (OCH3), 20.9 (COCH3); MALDI-MS: 1079.3
1108, 1051, 1027, 806, 736, 697 cmꢂ1 1H NMR (500 MHz, CDCl3):
;
d 7.41–7.08 (m, 35H, Ar-H), 7.08 (d, J = 9.0 Hz, 2H, Ar-H), 6.78 (d,
J = 9.0 Hz, 2H, Ar-H), 5.63 (d, J = 3.0 Hz, 1H, H-1B), 5.54 (s, 1H,
PhCH), 5.51 (s, 1H, PhCH), 5.50 (d, J = 3.5 Hz, 1H, H-1D), 5.45 (d,
J = 3.0 Hz, 1H, H-1A), 5.31 (s, 1H, PhCH), 4.76 (d, J = 8.0 Hz, 1H, H-
1C), 4.74 (d, J = 12.5 Hz, 1H, PhCH2), 4.64–4.52 (m, 3H, PhCH2),
4.50–4.45 (m, 5H, H-3D, H-5D, PhCH2), 4.39 (d, J = 12.5 Hz, 1H,
PhCH2), 4.35–4.30 (m, 1H, H-5A), 4.28–4.20 (m, 4H, H-3B, H-6aA
H-6aB, H-6aC), 4.18–4.14 (m, 2H, H-2C, H-3A), 4.07–4.00 (m, 3H,
,

1392
A. Santra et al. / Tetrahedron: Asymmetry 23 (2012) 1385–1392
H-4B, H-6bA, H-6bC), 3.95–3.92 (m, 2H, H-2D, H-5A), 3.91–3.88 (m,
2H, H-4C, H-4D), 3.82 (t, J = 9.5 Hz each, 1H, H-4A), 3.73–3.70 (m,
2H, H-3C, H-6bB), 3.71 (s, 3H, OCH3), 3.52 (dd, J = 10.0, 3.0 Hz, 1H,
H-2B), 3.34–3.32 (m, 2H, H-5B, H-5C), 3.25 (dd, J = 10.0, 3.0 Hz,
1H, H-2A), 0.78 (d, J = 6.0 Hz, 3H, CCH3); 13C NMR (125 MHz,
CDCl3): d 156.0–114.8 (Ar-C), 102.3 (C-1C), 101.9 (PhCH), 100.9
(PhCH), 100.7 (PhCH), 100.1 (C-1D), 98.5 (C-1B), 97.0 (C-1A), 82.4
(C-4A), 81.6 (C-3C), 79.3 (C-2D), 78.5 (C-5B), 76.4 (C-4C), 75.8 (C-
3D), 74.7 (PhCH2), 73.0 (C-4B), 72.7 (2 C, C-4D, PhCH2), 72.4 (PhCH2),
71.7 (C-3B), 71.4 (C-3A), 70.8 (PhCH2), 69.3 (C-6C), 69.2 (C-6A), 68.6
(C-6B), 66.5 (C-5A), 66.3 (C-2C), 64.1 (C-5D), 63.1 (C-5C), 61.9 (C-2A),
58.5 (C-2B), 55.6 (OCH3), 16.2 (CCH3); MALDI-MS: 1453.5 [M+Na]+;
Anal. Calcd for C80H82N6O19 (1430.56): C, 67.12; H, 5.77. Found: C,
66.93; H, 6.00.
at room temperature for 1 h. The solvents were removed under re-
duced pressure to give the product, which was further purified
over LH-20 using CH3OH–H2O (5:1, v/v) as eluant to give pure
compound 2 (290.0 mg, 62%). Glass; ½a D25
¼ þ6 (c 1.2, H2O); IR
ꢃ
(KBr): 3428, 2926, 2853, 1710, 1652, 1587, 1400, 1396, 1223,
1056, 996, 697 cmꢂ1
; d 6.94 (d,
1H NMR (500 MHz, D2O):
J = 9.0 Hz, 2H, Ar-H), 6.81 (d, J = 9.0 Hz, 2H, Ar-H), 5.30 (d,
J = 3.5 Hz, 1H, H-1A), 5.28 (d, J = 3.5 Hz, 1H, H-1B), 5.05 (d,
J = 3.5 Hz, 1H, H-1D), 4.47 (d, J = 7.5 Hz, 1H, H-1C), 4.07–4.00 (m,
4H, H-2A, H-2B, H-2D, H-3D), 3.91 (t, J = 9.5 Hz each, 1H, H-2C),
3.86 (dd, J = 10.0, 3.0 Hz, 1H, H-3B), 3.80–3.74 (m, 1H, H-5A),
3.76–3.74 (m, 2H, H-4B, H-4C), 3.70–3.65 (m, 2H, H-3C, H-4A),
3.64–3.53 (m, 7H, H-3A, H-6abA, H-6abB, H-6abC), 3.63 (s, 3H,
OCH3), 3.52–3.44 (m, 4H, H-4D, H-5B, H-5C, H-5D), 1.90, 1.89 (2 s,
6H, 2COCH3), 1.10 (d, J = 6.0 Hz, 3H, CCH3); 13C NMR (125 MHz,
D2O): d 174.3, 173.6 (2 COCH3), 154.6–115.0 (Ar-C), 102.0 (C-1C),
99.3 (C-1D), 97.1 (C-1B), 96.8 (C-1A), 76.3 (C-4D), 75.7 (C-4C), 74.9
(C-2C), 73.7 (C-5B), 73.5 (C-3B), 72.4 (C-4A), 71,8 (C-5D), 71.0 (C-
3A), 70.5 (C-5A), 69.6 (C-5C), 69.0 (C-4B), 68.6 (C-3D), 68.0 (C-3C),
66.8 (C-2D), 60.8 (C-6C), 60.5 (C-6A), 59.9 (C-6B), 55.8 (OCH3),
51.9 (C-2A), 49.1 (C-2B), 22.0 (COCH3), 21.9 (COCH3), 15.4 (CCH3);
MALDI-MS: 861.3 [M+Na]+; Anal. Calcd for C35H54N2O21 (838.32):
C, 50.12; H, 6.49. Found: C, 49.97; H, 6.70.
4.13. p-Methoxyphenyl (
pyranosyl)-(1?3)-(2-acetamido-2-deoxy-
syl)-(1?3)-2-acetamido-2-deoxy- -galactopyranoside 1
a
-L
-fucopyranosyl)-(1?2)-(b-
D-galacto-
a-D
-galactopyrano-
a-D
To a stirred solution of compound 15 (800.0 g, 0.56 mmol) and
20% Pd(OH)2–C (150.0 mg) in a mixture of CH2Cl2 (3 mL) and
CH3OH (3 mL) was added dropwise Et3SiH (1 mL, 6.26 mmol) at
room temperature for 30 min after which the reaction mixture
was allowed to stir at room temperature for 6 h. The reaction mix-
ture was filtered through a CeliteÒ bed and concentrated to dry-
ness. To a solution of the dry mass in CH3OH (5 mL) was added
acetic anhydride (0.2 mL) and the reaction mixture was kept at
room temperature for 1 h. The solvents were removed under re-
duced pressure to give the product, which was further purified
over LH-20 using CH3OH-H2O (5:1, v/v) as eluant to give pure com-
Acknowledgments
A. S. and T. G. thank CSIR, New Delhi for providing Senior and
Junior Research Fellowships. This work was supported by DST,
New Delhi (No. SR/S1/OC-83/2010).
pound 1 (300.0 mg, 64%). Glass; ½a D25
¼ þ19 (c 1.2, H2O); IR (KBr):
ꢃ
3416, 2927, 2854, 1713, 1650, 1585, 1406, 1398, 1221, 1149, 1087,
1056, 995, 695 cmꢂ1; 1H NMR (500 MHz, D2O): d 7.00 (d, J = 9.0 Hz,
2H, Ar-H), 6.86 (d, J = 9.0 Hz, 2H, Ar-H), 5.39 (d, J = 3.5 Hz, 1H, H-
1A), 5.12 (d, J = 4.0 Hz, 1H, H-1D), 4.99 (d, J = 3.0 Hz, 1H, H-1B),
4.54 (d, J = 8.0 Hz, 1H, H-1C), 4.42 (dd, J = 11.0, 4.0 Hz, 1H, H-2A),
4.17–4.08 (m, 3H, H-2B, H-2D, H-3D), 4.04 (dd, J = 10.0, 3.5 Hz, 1H,
H-3A), 3.97 (t, J = 7.6 Hz each, 1H, H-2C), 3.89 (dd, J = 10.0, 3.0 Hz,
1H, H-3B), 3.85–3.83 (m, 1H, H-5C), 3.80 (br s, 2H, H-4A, H-4B),
3.73 (dd, J = 10.0, 3.5 Hz, 1H, H-3C), 3.69 (s, 3H, OCH3), 3.67–3.60
(m, 7H, H-4C, H-6abA, H-6abB, H-6abC), 3.59–3.50 (m, 4H, H-4D, H-
5A, H-5B, H-5D), 1.97, 1.94 (2 s, 6H, 2 COCH3), 1.09 (d, J = 6.0 Hz,
3H, CCH3); 13C NMR (125 MHz, D2O): d 174.4, 173.7 (2 COCH3),
154.7–114.9 (Ar-C), 102.1 (C-1C), 99.2 (C-1D), 97.1 (C-1A), 93.2
(C-1B), 76.1 (C-5A), 75.0 (C-5B), 73.8 (C-3B), 73.5 (C-3C), 72.1 (C-
3A), 71.8 (C-5D), 71.5 (C-2C), 70.9 (C-5C), 69.6 (C-4D), 69.0 (C-4A),
68.8 (C-4B), 68.0 (C-2D), 66.7 (C-4C), 64.4 (C-3D), 61.1 (C-6C), 60.8
(C-6A), 60.7 (C-6B), 55.7 (OCH3), 49.0 (C-2B), 47.9 (C-2A), 22.1,
21.9 (COCH3), 15.3 (CCH3); MALDI-MS: 861.3 [M+Na]+; Anal. Calcd
for C35H54N2O21 (838.32): C, 50.12; H, 6.49. Found: C, 49.95; H,
6.73.
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4.14. p-Methoxyphenyl (
pyranosyl)-(1?3)-(2-acetamido-2-deoxy-
syl)-(1?3)-2-acetamido-2-deoxy- -glucopyranoside 2
a
-L
-fucopyranosyl)-(1?2)-(b-
D-galacto-
a-D
-galactopyrano-
a-D
To a stirred solution of compound 20 (800.0 mg, 0.56 mmol)
and 20% Pd(OH)2–C (150.0 mg) in a mixture of CH2Cl2 (3 mL) and
CH3OH (3 mL) was added dropwise Et3SiH (1 mL, 6.26 mmol) at
room temperature for 30 min after which the reaction mixture
was further allowed to stir at room temperature for 6 h. The reac-
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